That premise may have once seemed inconceivable, but the librarians at BiblioTech, a name that plays off the Spanish name for library, are quick to point out that their library isn't bookless — it's simply digital.

BiblioTech opened in September 2013 and had more than 103,000 visitors in its first year. While it houses no physical books, it has 48 iMac computers for visitors to use, and members can check out an e-reader for two weeks and read from a selection of 25,000 titles.

A simplified version of BiblioTech is located nearby in the Bexar County Courthouse, where jurors can borrow an e-reader to pass the time. This summer, a third digital library will open in a San Antonio housing project.

Bexar County Judge Nelson Wolff, who first conceived the idea of an all-digital library in 2011, said he wants to open the libraries in areas where low-income residents can access the technology.

The county will pay the San Antonio Housing Authority $1 a year to house the library, but even without the very affordable rent, BiblioTech is a bargain compared with many libraries.

The digital-only library was built, stocked and staffed for $2.2 million. About an hour away in Austin, the Texas capital's new downtown library has a budget of more than $100 million.

Florida Polytechnic University, which opened for classes in 2014 in Lakeland, Florida, features a fully digital library, and it's budgeted $60,000 to buy titles through software that allows students one free browse of a title. With the second click, the university purchases the e-book.

"Instead of the librarian putting books on the shelf that I think would be relevant, the students are choosing," Kathryn Miller, the university's director of libraries, told Reuters.

If a student wants to read an old-fashioned, tangible book, one can be requested on loan from one of Florida's 11 other public universities.

Before creating its library, the university consulted with digital libraries run by NASA and the University of Central Florida's medical school, and officials discovered that while going digital has its advantages, there are some downsides.

With technology and information constantly evolving, it can be difficult to keep up, and while digital books tend to be more affordable, many licensing agreements require annual payments.

"In the past, you could buy a reference book and it could sit on your shelf for 120 years," said Carrie Russell, a policy analyst for the American Library Association.

A library with no books to pick up and browse may seem strange, but Wolff says BiblioTech hasn’t received any complaints about its lack of physical books. Still, he doesn't think digital libraries are a threat to their predecessors.

"I think there will always be some role for printed books in libraries," he said.